Hydraulic oil composition

ABSTRACT

AN IMPROVED ANTI-LEAK HYDRAULIC OIL OF THE GEL-THICKENED TYPE COMPRISES AN EFFECTIVE AMOUNT OF A LITHIUM SOAP (E.G. 0.1-1% LI STEARATE) OR AN ALUMINUM SOAP (E.G. 0.5-2% AL STEARATE), OR MIXTURES OF SUCH SOAPS, AND A BASE OIL HAVING A VISCOSITY IN THE RANGE OF 80-800 SUS AT 100*F. AND AN ANILINE POINT IN THE RANGE OF 150-170* F., SAID BASE OIL COMPRISING AT LEAST ONE HYDROREFINED NAPHTHENIC OIL HAVING A VISCOSITY IN THE RANGE OF 40-12,000 SUS AT 100*F. THE HYDRAULIC OIL CAN ALSO CONTAIN AN ANTI-RUST AGENT (E.G. 0.02-2%) BARIUM PETROLEUM SULFONATE, AN ANTI-OXIDANT (E.G. AN AMINE TYPE) AND AN ANTIWEAR (E.G. 0.1-5% ZINC DIALKYL DITHIOPHOSPHATE).

United States Patent Offiee 3,694,363 Patented Sept. 26, 1972 Int. Cl. C09k 3/00 US. Cl. 252-72 11 Claims ABSTRACT OF THE DISCLOSURE An improved anti-leak hydraulic oil of the gel-thickened type comprises an effective amount of a lithium soap (e.g. 0.l-1% Li stearate) or an aluminum soap (e.g. (LS-2% Al stearate), or mixtures of such soaps, and a base oil having a viscosity in the range of 80-800 SUS at 100 F. and an aniline point in the range of ISO-170 F., said base oil comprising at least one hydrorefined naphthenic oil having a viscosity in the range of 40-12,000 SUS at 100 F. The hydraulic oil can also contain an anti-rust agent (e.g. 0.02-2%) barium petroleum sulfonate, an anti-oxidant (e.g. an amine type) and an antiwear (e.g. 0.1-5% zinc dialkyl dithiophosphate).

CROSS REFERENCE TO RELATED APPLICATIONS The following patents and applications are related to the disclosure of the present application in that they disclose methods of obtaining distillate oils and hydrorefined oils which can be used to make the hydraulic oil composition of the present invention.

US. 3,462,358 issued Aug. 19, 1969; Ser. No. 636,493 filed May 5, 1967; US. 3,502,567 issued Mar. 24, 1970; Ser. No. 730,999 filed May 22, 1968; U.S. 3,619,414 issued Nov. 9, 1971; Ser. No. 850,716 (now abandoned in view of continuation-in-part Ser. No. 175,775 filed Aug. 27, 1971): Ser. No. 850,717 (now abandoned in view of continuation-in-part Ser. No. 228,832 filed Feb. 24, 1972); US. 3,654,127 issued Apr. 4, 1972; Ser. No. 873,008 filed Oct. 31, 1969; Ser. No. 874,087 filed Oct. 27, 1969; and Ser. No. 22,295 filed Mar. 24, 1970. The disclosure of all of these applications and patents is hereby incorporated herein.

BACKGROUND OF THE INVENTION The industrial hydraulic oil market is continuing to grow at a rapid pace. Accompanying this growth is the demand for better lubricant properties. Specific improvements are needed to cope with trends towards more severe operating conditions and better pollution control. In the response to these requirements, research has made important advances in upgrading antiwear and antileak properties. Wear-resistant oils can alleviate the equipment problems and failures caused by increased pressures and temperatures, shock loading, reduced tolerances, etc. Antileak oils can decrease the undesirable loss of lubricants. Not only do these latter oils reduce consumption, but they help curb the pollution of our natural waters.

Water pollution by industrial oil is a problem which exists in spite of the corrective elforts by industry and expenditures of large amounts of money. Waste oil is not generated intentionally. In most cases it is a problem which plant management has recognized and is constantly attempting to effectively eliminate. Certain industrial machines are prolific leakers and, operating at the normal high levels of production, cannot be shut down for repairs.

Oil can enter sewage lines if the equipment leaks are allowed to drain off directly. Another source of water pollution results from internal equipment leakage where oils are mixed with the water or soluble cutting oil coolants. When the level of oil contamination becomes too high, the cooling properties are ruined and the water or soluble oil systems are drained (see U.S. News and World Report, pages 42-45, Apr. 3, 1967 and Priestly, J.J., Civilization, Water and Wastes Chemistry and Ind. 12, 355-363 (1968)). In the past, these water-containing mixtures have sometimes been dumped directly into sewage lines or streams. Oil in the streams and rivers, from whatever source, makes water processing very difficult for reuse by humans and also disrupts the natural marine life cycle.

There are a great number of aspects to the control of pollution. This invention is concerned with one specific area, that of antileak hydraulic oils. By reducing leakage at the source, waste oil can be greatly minimized. This new class of hydraulic oils, however, must not sacrifice other properties to the degree that lubrication and machinery protection are not satisfactory (see Cutting Fluids, Lubrication 42 (4) 49-60 (1956)). The present antileak hydraulic oil helps control pollution and also is completely satisfactory from the standpoint of other performance requirements.

Antileak oils are lubricants which have been specifically designed to reduce leakage. The word leakage is used herein to refer only to undesired lubricant loss. Many operations require controlled lubricant consumption such as for moving shafts, etc.

Wear-resistant (WR) oils combine the excellent stability, and rust-resistance properties of industrial turbine oils.

The need for these oils arose because of an increase in the number of mobile equipment pump breakdowns. Overloads on the engine-drive pumps, lubricated with conventional turbine oils, caused the breakdowns.

Experiments showed that pumps lubricated with MS oils would operate under equivalent conditions for 10 to 100 times as long as conventional turbine oils (Leslie, R. L., Views on Petroleum Oils for Hydraulic Sewage," National Petroleum Refiners Association Pub. Tech. 65-34L, September 1965).

However, crankcase oils were not the ideal solution for in-plant systems. These fixed installations are subject to water contamination. The high detergent properties of crankcase oils made it almost impossible to remove water from a contaminated system. This established a need for new WR oils.

SUMMARY OF THE INVENTION An improved antileak hydraulic oil of the gel-thickened type comprises an effective amount of a lithium soap (e.g. 0.11% Li stearate) or an aluminum soap (e.g. 0.5-2% Al stearate), or mixtures of such soaps, and a base oil having a viscosity in the range of -800 SUS at F. and an aniline point in the range of ISO- F., said base oil comprising at least one hydrorefined naphthenic oil having a viscosity in the range of 40-12,000 SUS at 100 F. The hydraulic oil can also contain one or more of the following: an antirust agent (eg, 0.02-2% typically 0.2% barium sulfonate), an antioxidant (e.g. 0.5-1% of an amine type), an antifoam (e.g. 0.05-1% of a silicone type) and an anti-wear (e.g. 0.1-5%, typically 0.3-2%, zinc dialkyl dithiophosphate).

The hydraulic oil can show good antiwear and antileak performance and good hydrolytic and oxidation stability in the ASTM D943 turbine oil stability test (TOST).

The base oils preferably contain less than 80 p.p.m. of basic nitrogen and can be those described in the previously cited applications of Mills et al. and, more preferably, are blends of two or more hydrorefined naphthenic oils (e.g. a blend of a 100 SUS at 100 F. hydrorefined naphthenic oil and a 2500 SUS at 100 F. hydrorefined naphthenic oil).

In the hydraulic oil of the present invention, leakage reduction is achieved by designing into the lubricant the ability to maintain good rubber seal condition and to obstruct small leaks with retardant materials (e.g. Li or Al soaps or polymers). Plant trials have been conducted comparing the performance of the antileak hydraulic oils of the present invention to current, standard products. Lubricant loss was lowered as much as 88% by the leak resistant formulations. These antileak hydraulic oils of the present invention also have good overall properties and have performed well in many types of plant equipment.

FURTHER DESCRIPTION The hydrocarbon base oil can also contain a low nitrogen content paraflinic distillate or solvent raffinate oil, a hydrorefined paratfinic distillate or raflinate, a viscosity index improver (e.g. high molecular weight polybutene or an acylate) a polycyclic aromatic concentrate (such as cycle stock) to adjust the 335 UVA of the base stock (which preferably is in the range of 001-04, more preferred 0.02-0.2) and an unrefined naphthenic distillate or a naphthenic acid-free naphthenic distillate.

The preferred amount of gelling agent to add to a given base oil can be determined from an experimentally obtained soap in oil curve. That is various amounts of soap are added to base oil samples (which can also include all of the other additives) and the viscosity of the soap-oil samples is determined. The results are plotted as a viscosity versus concentration curve. In such a curve, a point will be found where the viscosity suddenly increases greatly. This will be the minimum concentration of soap which should be put into the oil for antileak protection. Generally, about 0.1% more soap than this minimum concentration should be put into the oil. The maximum amount of soap (or other gelling agent) will be where the solution lumps-up or becomes non-homogeneous.

To reduce equipment ieakage, it is important that elastomeric seals and gaskets maintain a slight positive swell and remain pliable. Shrinkage and hardening allow oil to bypass. Certain base oils can help to keep the seals working properly.

A good test for judging if a base stock will properly condition the most commonly used seals, i.e. Buna N and neoprene, is the Aniline Point (ASTM D611). This test measures the solubility temperature of aniline and the lubricant. The aniline point is, therefore, a measure of solvency characteristics. The higher the aniline point, the poorer the solvency of the lubricant. Data obtained for the percent swell for Buna N and neoprene seals for a series of 250 SUS at 100 F. oils having aniline points ranging from 150 F. to 230 F. show, that to obtain a small positive swell with the seals tested, the base oil should have and aniline point between 150 F. and 170 F. Lublicants which are mostly paraflinic in structure have high aniline points and will shrink the rubber and make it hard. This permits the lubricant to leak. On the other hand, if the aniline point is below 150 F., excessive swell often occurs and the seal may be cut and torn by the rubbing surface, thereby allowing lubricant to bypass. This correlation does not necessarily apply to lubricants which contain seal conditioning additives.

Note that such prior art as US. Pat. 2,408,983 (which at column shows an aniline point of 178" F.) and US. 2,616,854 (which shows a range of l75190 F.) lead the art away from our preferred range of l50l70 F.

Besides utilizing a base oil which properly conditions the rubber seals and gaskets, leakage can also be reduced by restricting small openings with leak retardant materials. The leak retardant must be carefully selected so that other properties of the lubricant are not harmed. There are two basic types of antileak additives presently being used. The first is the polymeric type which includes materials having molecular weights greater than several hundred thousand (e.g. polybutene). The second involves gelling agents (e.g. organic salts of polyvalent metals or soaps") which can have molecular weights of about three hundred.

It has been postulated that the polymeric materials develop a more rigid structure in areas of low shear rates, such as the threads of a leaky coupling. The viscosity, therefore, increases and flow is hindered from the high pressure zone.

Gelling agents are believed to perform in a different manner. That is, they build up fibers or log jams in small openings, thereby barricading them and preventing fluid flow.

Both of these types of antileak additives shear down temporarily when subjected to pump, valve, etc. operations. Permanent shear loss is also experienced to a limited degree. Because this does occur, the equipment is able to operate satisfactorily without clogging problems.

There are no known products which completely stop leakage. One reason for this is that the types of leak retardants which can be used are limited by other performance characteristics. The antileak component must be a material which will not cause plugging in filters as small as 5 microns or interfere with servo-valve operation where clearances are extremely critical. Other properties of the lubricant itself, such as the oxidation stability, foam resistance, etc., must not be sacrificed. Leaks vary considerably in size and nature. The efficiency of the antileak hydraulic oils is influenced by the type of leak. Small openings may be closed completely whereas large openings or badly deteriorated seals may not be affected to any measurable degree.

In the following examples, as in the rest of this application, all percentages are by weight.

ILLUSTRATIVE EXAMPLES The best wa to evaluate new formulations is in the actual machinery in which leak problems are encountered. There is presently no standard way to measure antileak properties in the laboratory. A laboratory method has been devised, however, which appears to correlate with field experience. This test has been useful in measuring good versus bad antileak oils or improvements over a given reference oil. The reference oil can be, for example, a rust and oxidation (R&O) inhibited paraffinic hydraulic oil. This R&O reference contains all of the necessary additives to guarantee good lubricant performance but incorporates no leak retardants.

The apparatus in which leakage characteristics are measured is a U-shaped combination of /3" iron nipples, union sleeves, and elbows. They are joined together by hand tightening in a U-shape and then spot welded to hold in a fixed position. One end of the U is capped, the other end is connected to a pressure source. The procedure utilizes a 300 cc. oil sample. The system is pressurized to 30 p.s.i. with nitrogen and allowed to stand for one hour. The oil which has dripped out at the end of this period is collected and weighed.

As with most screening tests, this method can only predict whether the oil is better than another. It cannot indicate the degree of improvement to be provided. Nothing but a large amount of field experience can supply this information.

EXAMPLE I Polymeric type antileak hydraulic oils The incorporation of proper polymers into hydraulic oils at concentrations as high as 5% can provide leakage protection. As can be seen in Table I, a typical product containing a high molecular weight butene polymer also has good overall properties. The base oils, which are naphthenic in nature, have an aniline point of 152 F. and generally provide good rubber seal conditioning. Water separation, foam resistance, rust protection are all acceptable. The oxidation stability, as measured by the ASTM D943 procedure, is 1,250 hours. Leakage resistance, according to the laboratory test is approximately 41% less than that of a normal R&O hydraulic oil.

Two field trials were run with the polymeric antileak hydraulic oil. The results of these equipment evaluations are listed in Table In the first field trial listed, three breaches were run for a period of two months at each of three separate plant locations. The broaches were first run with the R&O hydraulic oil to determine baseline data. The polymeric antileak oil was then added to these same machines and consumption characteristics measured. As can be seen, the three divisions reported improvements of 46%, 88%, and 50%, respectively. The second trial listed in Table II was run on a total plant basis. All machines using R810 hydraulic oil were studied for consumption during a six month period. These same machines were then charged with the polymeric antileak hydraulic oil for an equivalent six month period. After the one year trial, this plant measured a reduction in lubricant consumption of 28%. Table III lists twelve machines in the second plant trial which had the largest amount of leakage with the R&O type hydraulic oil. The machines covered a wide range of operations. In these pieces of equipment, the leakage reduction aiforded by the polymeric antileak hydraulic oil was 39%, significantly more than the percentage reported for the total plant. Good leakage reduction is obtained with 16% polybutene (typically 2%).

The polymeric antileak lubricant after the field trials had experienced only the normal amount of degradation. Filter and valve operations were completely satisfactory. The one final property which had changed more than that of the R&O hydraulic oil was viscosity. The polymer loss by sheardown caused a viscosity decrease of approximately This loss did not cause any performance problems.

EXAMPLE II Gel type antileak hydraulic oils An antileak hydraulic oil according to the present invention was compounded using lithium stearate as a gel type leak retardant.

The gel type antileak hydraulic oil composition had a SUS viscosity of about 250 at 100 F and was prepared from a 200 SUS (at 100 F.) base oil containing 56 p.p.m. of basic nitrogen and obtained by blending 25% of 2400 SUS (at 100 F.) hydrorefined naphthenic oil and 75% of 100 SUS (at 100 F.) hydrorefined naphthenic oil. Both hydrorefined naphthenic oils were obtained from naphthenic acid-free naphthenic distillate by hydrogenation at 625 F., 1200 p.s.i.g. of 80% hydrogen, 0.2 LHSV with a presulfided Ni-Mo-oxide catalyst. In addition to the base oil, the hydraulic oil contained 0.25% Li stearate, 0.25 of an amine type antioxidant (Du Pont Ortholeum), 0.1% of a defoamer (.Dow Corning Silicone), 0.2% of a neutral barium petroleum sulfonate antirust agent, and 0.7% Zn dialkyl dithiophosphate (Elco 114). The Zn dialkyl dithiophosphate imparts especially useful antiwear and antioxidant properties to the hydraulic fluid and has excellent hydrolytic stability. The alkyl group of this additive can vary considerably, depending on the manufacturer; however, all such presently commercially available Zn dialkyl dithiophosphate antiwear additives can be used in the fluid of the present invention.

Specific gelling agent (e.g. Li or A] soaps) appear to be more efiicient than the polymers in reducing leakage at concentrations up to 3%. The Al soaps are less hydrolytically stable than the Li soaps. Lubricants containing these materials are, however, also somewhat less stable to oxidation. As is shown in Table IV, the overall properties of the gel containing hydraulic oil are good. A hydrogenated naphthenic type base oil with an aniline point of 160 F. was used to provide seal swell. Oxidation stability, as measured by the ASTM D943 procedure, is about 300 hours less than the polymeric version but about 200% better than a comparable oil containing naphthenic acid-free naphthenic distillate instead of the hydrorefined oil. The leak resistance of the gel type oil 6 made from the hydrorefined base stock is twice as good as measured in laboratory equipment.

Field trial data with the gel antileak hydraulic oil of the present invention are listed in Table V. Three presses were tested, on a horizontal type, and the other two vertical. As shown, these presses were operated from 880 hours to 1,944 hours. Leakage reduction when compared to the R&O hydraulic oil was 55%, and 60%, respectively. These values are higher than the reductions reported for the polymeric antileak hydraulic oil. Filter and valve performance were completely acceptable. After this trial the condition of the product was excellent. There was no significant viscosity or acid buildup. A viscosity loss of about 15% occurred due to the sheardown of the gel, but there was still enough of the leak retardant present to maintain good leakage reduction.

Actual equipment testing has shown that polymeric antileak hydraulic oils can reduce losses by 28 to 88%. The gel containing antileak hydraulic oils of the present invention are more efiicient with reductions of 55 to 85% in plant equipment. 1

TABLE LPOLYMERIC TYPE ANTILEAK HYDRAULIC OIL LUBRICANT PROPERTIES R and 0 Antileak ASTM hydrauhydrau- Test method lic 011 he oil Viscosity:

S US/ F 250 242 SUS/210 F. 50. 4 45. 3 Index 102 34 Cs./l00 F. 53. 9 52.1. (ls/210 F 7.4 5. 82 Flash, Goo s... 440 335 Fire, COC, FL... 495 385 Pour, F D97 0 -25 Color D1500 2.0 2. 25 Gravity, AP D287 31. 2 21,2 TAN, mg. KOII/g. D064 0.07 0, 0 Copper strip, class. D130 1 1 Aniline point, F D611 230 152 Dimulslbllity/lBO" F: Separation, D1401 10 20 rnin. Foam, tendeneylstabllity:

Sequence I. ml 2010 5/(] Sequence II ml. 2010 25/0 Sequence II ml- 20/0 211/0 Rust, syn. sea water" 6653 Pass Pass Oxidation stability, hr D943 1 300 1, 250 Leak resistance:

Gms. leaked 65 Reduction, percent 41 1 To 2.0 TAN end point.

TABLE II.POLYMERIC TYPE ANTILEAK HYDRAULIC OIL PLANT TRIAL DATA Consumption, gallons R and 0 Antileak hydraulic hydraulic Percent oil oil reduction Number 1 plant trial: Per breach per week 1 at- 5. 7 3. 1 46 23. 1 2. 7 B8 10. 0 5. 0 60 Number 2 plant trial:

Total plant usage 2 3,131,667 2, 242,766 28 Per unit manufactured .98 75 24 1 2 month duration. 2 6 month duration.

TABLE III.-POLYMERIC ANTILEAK HYDRAULIC OIL NO. 2 PLANT TRIAL LEAKAGE COMPARISONS Most critical machines average weekly consumption, gal.

R and 0 Antileak hydraulic hydraulic Type equipment oil oil Total 1, 184 Percent, reduction TABLE IV.GEL TYPE ANTILEAK HYDRAULIC OIL LUBRICANT PROPERTIES RandO Antileak ASTM hydrauhydrau- Tcst method 110 oil lic oil Viscosity:

SUS/100 F D2161. 250 258 SUS/210 F D2161 50.4 45. 5 102 28 Aniline point, F 230 160 Demulsibilltyll30 F.: Separation, D1401 10 25 min.

Foam, tendency/stability D892 Sequence 1, /0 5/0 Sequence 11 ml.. 20/0 m Sequence Hi, ml 2010 5/0 Rust, syn salt water Pass Pass Oxidation stability, hr 1, 300 900 Leak resistance:

Grns. leaked 20 Reducation, percent 82 I To 2.0 TAN end point.

TAB LE V.-GEL TYPE ANTILEAK HYDRAULIC OIL PLANT TRIAL DATA 1 Horizontal press. 3 Vertical press.

The invention claimed is:

1. A soap thickened antileak hydraulic ail consisting essentially of an efiective amount for thickening of lithium stearate and a hydrocarbon base oil having a viscosity in the range of 80-8000 SUS at 100 F. and an aniline point in the range of ISO-170 F., said base oil consisting essentially of a hydrorefined naphthenic oil or a blend of two or more hydrorefined naphthenic oils having a viscosity in the range of 12,000 SUS at 100 F.

2. Hydraulic oil according to claim 1 wherein at least one said hydrorefined naphthenic oil contains less than 80 p.p.m. of basic nitrogen.

3. Hydraulic oil according to claim 1 and containing a zinc dialkyl dithiophosphate antiwear agent.

4. Hydraulic oil according to claim 3 and containing in the range of 0.11% lithium stearate, in the range of 0.022% neutral barium petroleum sulfonate and in the range of 0.1-5 zinc dialkyl dithiophosphate.

5. Hydraulic oil according to claim 1 and containing in the range of 0.3-2% zinc dialkyl dithiophosphate.

6. Hydraulic oil according to claim 1 and wherein said base oil has a viscosity at 100 F. in the range of 150-350 SUS.

7. Hydraulic oil according to claim 6 and containing in the range of 0.11% lithium stearate.

8. Hydraulic oil according to claim 1 wherein said base oil is a blend of at least two hydrorefined naphthenic oils.

9. Hydraulic oil according to claim 1 wherein said base oil contains less than p.p.m. of basic nitrogen.

10. Hydraulic oil according to claim 1 and wherein said base oil consists of said hydrorefined naphthenic oil.

11. Hydraulic oil according to claim 1 wherein said base oil contains in addition a member selected from low nitrogen content paralfinic distillate, low nitrogen content paraflinic solvent raflinate oil, hydrorefined paraflinic distillate, hydrorefincd paraffinic rafiinate, polycyclic aromatic concentrate, unrefined naphthenic distillate, and naphthenic acid-free naphthenic distillate.

References Cited UNITED STATES PATENTS 2,074,039 3/1937 Zimmer et al. 87-9 3,481,863 12/1969 Donaldson et al 208-210 2,489,300 11/1949 Leyda 25276 X 3,383,312 5/1968 COppOck 252-35 X 3,203,896 8/1965 Latos et a1 252 X 3,360,468 12/1967 Dieman et al 252-75 2,528,348 10/1950 Denison et al. 252-75 OTHER REFERENCES Georgi: Motor Oils and Engine Lubrication," (1950), pub. by Reinhold Pub. Co., pp. 108, 153, 154.

LEON D. ROSDOL, Primary Examiner H. A. PITLICK, Assistant Examiner US. Cl. X.R. 

